In recent years, the screw or the bolt employing to stud on caulked members is strictly required physical conditions after caulking as well as finishing accuracy not to damage the quality of members employed.
However, upto now, as seen in the field, in particular to speak of panels for the automotive body and the like, the screw is spot welded or seamed by studding before or after painting or plating on the surface of caulked panels at process of caulking thin steel plates.
In case, a coloured steel panel is used as the caulked member; the part surrounding to the spot after welding is changed its colour and becomes difficult to correct finishing on the surface of the member same as before, and it requires an extra cleaning process when the screw is welded before such painting.
According to the method of studding in the later, wherein the screw having a structure with a flange is employed, and the head of bolt must be caulked after inserting into the member, extra processes such as deciding position, drilling and then studding are required.
Above conventional type stud screws, in both cases, could not dissolve concern that may occur blurs of welding or slipping off and turning after caulking besides the working efficiency was decreased.
Accordingly, it is an object of the present invention to provide the structure of the caulking bolt to get rid of such defects of conventional types without drilling any on the caulking panels and also, making the stud finished in one process to admit even a thin panel.
It is another object the present invention to provide the structure of said bolt, wherein the head of bolt is stabilizingly extended after caulking to firmly seam with the panels and to satisfy desired the physical requisite.